There's a cutaway (or maybe just partly dismantled? Merlin on display at the private warbird museum in Pungo near VA Beach. Dual overhead cams, hemi heads, four valves and two spark plugs per cylinder, two superchargers, fuel injection. Basically all the modern stuff was fully in-effect.
I think it had 6:1 compression.
When I look at that engine I marvel at how little power it made: 27 liters was good for only 1700-odd horses.
But still good enough for 1942!
The other old engine that fascinates is the Offy.
A 1920s design! With dual overhead cams! That won Indy in 1935....and in 1968!!!
—and also '64, '63, '62, '61, '60, '59, '58, '57, '56, '55, '54, '53, '52, '51, '50, '49, '48 and '47.
"Then Offy had another golden era, winning five years in a row from 1972 to 1976 with a turbocharged 2.6-liter (159 cubic inch) engine format."
When we talk about rapid development of new and better internal combustion engine designs that win at the highest levels of competition, I think we need to remember the Offenhauser/Miller L4, while remembering that its DOHC design dated from the 1910s or earlier, and maybe nodding our heads to those would improve that design. (Especially the oiling system).
Worth noting too that Harry Miller gave Ed Iskendurian his start in the cam grinding business, and that one of the most salient features of the Offy was how easily the camshafts could be swapped out to better match the car it was in and track it was on.
Main bearings? Well, no...you needed to heat the whole block up to press new ones in. But cams could be wrenched out and replaced in a pit stop.
